As is well-known, when the life of a fluorescent lamp comes to an end, the ballast makes the lamp work continuously, thus causing over-heat of the lamp and generating discharge “smog”, meanwhile, a very high voltage is generated at the cathode of the lamp to put the lamp and the ballast in an abnormal and dangerous state. Therefore, the End of Lamp Life detect circuit is more and more widely used in the electronic ballast controlled by an Application Specific Integrated Circuit (ASIC) or a Microcontroller.
Meanwhile, reducing the output power of the high-performance electronic ballast when full output is unnecessary can not only functions to save energy and prolong the lifetime of the lamp, but also change the visual effect. Thus it is particularly meaningful to integrate a dimming selection function in the electronic ballast in this time when energy saving is gaining more and more attention.
However, in order to simultaneously achieve the above two functions in the electronic ballast, by use of the existing known circuits, there is no other choice but to integrate the two kinds of protection circuits at the same time, this not only increases the cost, but also requires complicated circuits that include a lot of elements and components.